Jakarta. Several people have died and dozens were injured in a series of explosions that rattled Surabaya and Sidoarjo in East Java on Sunday (13/05) and again on Monday.

Here are some facts the Jakarta Globe compiled about the incidents:

When and where did the attacks occur?

The first suicide bomb attack took place at 7.30 a.m. on Sunday at the Santa Maria Tak Bercela Catholic Church in Jalan Ngagel, Surabaya.

A second attack occurred 15 minutes later at the Protestant Christian Church in Jalan Diponegoro, Surabaya.

The third bombing occurred another 15 minutes later at the Surabaya Central Pentecostal Church in Jalan Arjuna, Surabaya.

A homemade bomb explodes at 9.15 p.m. on Sunday on the fifth floor of the Wonocolo low-cost apartment complex in Sidoarjo.

A suicide bombing occurred at 8.50 a.m. on Monday at the entrance of the Surabaya Police headquarters in Jalan Sikatan.

Who did it?

The first attack was carried out by a 17-year-old male, identified by the initials Y.F., and F.H., his 15-year-old brother.

The second bombing was carried out by 42-year-old P.K. and her two daughters, F.S. (12) and F.R. (9). P.K. is also the mother of the two males involved in the first attack.

The third bombing was carried out by 46-year-old D.O., the husband of P.K. and father of the children involved in the first two attacks. The family resided in Surabaya.

The explosion in Sidoarjo occurred while a homemade bomb was being assembled by A.W. who was killed in the incident, along with his wife P.S. and their eldest son R.A.R. The remaining three children were injured and taken to a police hospital in Surabaya. A.W. and D.O. were friends.

The attack on the Surabaya Police headquarters was carried out by a family of five, headed by T.M., according to National Police chief Gen. Tito Karnavian and East Java Police chief Insp. Gen. Machfud Arifin. Four adults, including a woman who carried the bomb, died in the attack. Their 8-year-old daughter was injured in the blast and taken to a police hospital in Surabaya.

How many casualties were there?

The three church bombings in Surabaya claimed the lives of 14 people, including the six attackers, while 43 people were injured.

The Sidoarjo blast claimed three lives, while three people were injured.

Monday's attack on the Surabaya Police headquarters claimed the lives of the four attackers, while 10 bystanders, including four police officers, were injured.

Who was responsible for the attacks and what were their motives?

According to the police, all the perpetrators had links with Jemaah Ansharut Daulah (JAD), a group affiliated to Islamic State. The person identified as D.O., who carried out the third church attack, was the leader of JAD's Surabaya cell.

The group is believed to have carried out the attack on the instruction of Islamic State, which requires followers around the world to commit acts of terror.

Members of JAD may also have attacked the police in retaliation for the arrest of their national leader, Aman Abdurrahman, and Zainal Anshory, leader of the group's East Java branch.

Aman Abdurrahman is currently on trial for several bombings in the country in recent years, including the deadly January 2016 attack in Jalan M.H. Thamrin, Central Jakarta.

Zainal Anshory was arrested about five months ago for funding the illegal purchase and smuggling of weapons from the Philippines to Indonesia.

What kind of explosives did they use?

According to the National Police chief, the attackers filled pipes with highly explosive triacetone triperoxide (TATP) and modified them to have different effects and explosive power, such as by adding gasoline.

The explosive, known as "Mother of Satan" because of its high susceptibility to accidental detonation, is commonly used by Islamic State in Iraq and Syria.

What steps have the police taken?

Within six hours after the church bombings, a police forensic team managed to identify the perpetrators. This was also done after the two other incidents.

Police have since identified members of the group who were planning to carry out more attacks.

Police have also captured more than 10 members of the group. A man identified as B.S., the second in command of JAD's Surabaya cell, was fatally shot during a police raid at his house in Sidoarjo on Monday.

What is being done to prevent future attacks?

President Joko "Jokowi" Widodo has called on members of the House of Representatives to speed up the finalization of a revision to the 2003 Antiterrorism Law, or he may issue a government regulation in lieu of law to address the matter.

Civil society groups have condemned the acts of terror and called on Indonesians to oppose all forms of radicalism.